Mike is absolutely correct.
If your snakes are feeding regularly, they do not need water to hydrate themselves.
They get all of their essential liquids from their food.
The whole watering dish ad-lib is a luxury of captivity. And if your snakes are drinking daily, you're probably not feeding often enough or your enclosure isn't humid enough....
Imagine the number of BPs in Africa making daily runs to the watering hole..... It's probably close to zero.